Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 98274 — Mount Vernon, WA

ZIP code 98274 (Mount Vernon, Skagit County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is April 22 and the first fall frost October 19.

Where ZIP 98274 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone8b15 to 20 °F
Coldest night−9.4 to −6.7 °C
Last frostApr 22
First frostOct 19
2012 zone8a

Was 8a on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 8b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mount Vernon, WA…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Mount Vernon, WA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 22median — 50% chance of a later frost
Safe for tender plantsMay 6only 10% chance of frost after
First fall frostOctober 19median — 10% chance by Oct 3
Growing season181 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 25 and returns around November 3.

From the NOAA station Arlington, WA — 11 miles away, elevation 102 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 98274

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 11 – Mar 25
SpinachSow outdoors · Mar 11 – Apr 1
Broccoli, cabbageStart indoors · Feb 11 – Feb 25
Broccoli, cabbageTransplant · Apr 1 – Apr 15
Onion setsPlant outdoors · Mar 25 – Apr 8
PotatoesPlant outdoors · Apr 1 – Apr 15
LettuceSow outdoors · Mar 25 – Apr 8
Carrots, beetsSow outdoors · Apr 1 – Apr 15
TomatoesStart indoors · Feb 25 – Mar 11
TomatoesTransplant · Apr 29 – May 13
Peppers, eggplantStart indoors · Feb 11 – Feb 25
Peppers, eggplantTransplant · May 6 – May 20
BeansSow outdoors · Apr 29 – May 13
Sweet cornSow outdoors · Apr 29 – May 13
Cucumbers, squashSow outdoors · Apr 29 – May 13
Fall lettuce, spinachSow outdoors · Aug 24 – Sep 7
GarlicPlant cloves · Oct 5 – Nov 9
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 22) and first fall frost (Oct 19) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 98274 came on Feb 22 — 27 days earlier than the 1991–2020 average (Mar 21).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 8b in Washington

614 plants native to the lower 48 states, recorded in Washington, and rated by the USDA to survive 15 °F or colder — the bottom of zone 8b. Each links to its USDA PLANTS profile.

Trees 32

Alaska cedar75 ft · blooms mid spring · low shade tolerance · to −22 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fbigleaf maple60 ft · blooms mid spring · medium shade tolerance · to −14 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °F

Shrubs 114

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °FBarclay's willow15 ft · high shade tolerance · to −43 °F

Wildflowers & perennials 293

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °F

Grasses 157

Alaska brome5 ft · blooms late spring · low shade tolerance · to −18 °FAlaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °FAmerican beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °F

Vines 3

riverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Ftrumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °Fwestern white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Mount Vernon, WA.

Soil in Mount Vernon, WA

The soil mapped at the center of ZIP 98274 is Chuckanut — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH4.5strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Chuckanut gravelly ashy sandy loam, 30 to 65 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 98274; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Vernon, WA

Summer high78 °Faverage high, August
Winter low28 °Faverage low, February
Hot days5days a year at 90 °F or more
Freezing nights94nights a year at 32 °F or less
Growing degree days1,458base 50 °F — the season’s usable heat
Longest day16 h 06 mindaylight on June 21
Shortest day8 h 19 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation49 inper year, rain and melted snow
Snowfall4 inper year; 3 days with snow on the ground

Average high and low, by month

20°30°40°50°60°70°80°90°32 °FJanuary: average high 47 °F, low 29 °F 47°29° JanFebruary: average high 51 °F, low 28 °F 51°28° FebMarch: average high 54 °F, low 32 °F 54°32° MarApril: average high 60 °F, low 35 °F 60°35° AprMay: average high 67 °F, low 41 °F 67°41° MayJune: average high 71 °F, low 45 °F 71°45° JunJuly: average high 77 °F, low 48 °F 77°48° JulAugust: average high 78 °F, low 47 °F 78°47° AugSeptember: average high 72 °F, low 42 °F 72°42° SepOctober: average high 61 °F, low 37 °F 61°37° OctNovember: average high 52 °F, low 31 °F 52°31° NovDecember: average high 46 °F, low 28 °F 46°28° Dec

Precipitation by month inches · ❄ = snowfall

0″2″4″6″8″January: 5.92 in precipitation, 0.8 in snowfall 5.9❄1 JanFebruary: 4.42 in precipitation, 0.7 in snowfall 4.4❄1 FebMarch: 5.00 in precipitation, 0.4 in snowfall 5.0 MarApril: 4.34 in precipitation 4.3 AprMay: 3.43 in precipitation 3.4 MayJune: 2.66 in precipitation 2.7 JunJuly: 1.15 in precipitation 1.1 JulAugust: 1.34 in precipitation 1.3 AugSeptember: 2.49 in precipitation 2.5 SepOctober: 4.94 in precipitation 4.9 OctNovember: 7.15 in precipitation, 0.2 in snowfall 7.2 NovDecember: 6.15 in precipitation, 2.2 in snowfall 6.2❄2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Arlington, WA (11 mi away); precipitation: Arlington, WA (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 8b.

982358b
Clearlake, WA · 9 mi
982388b
Conway, WA · 9 mi
982738b
Mount Vernon, WA · 11 mi
982928b
Stanwood, WA · 11 mi
982878b
Silvana, WA · 11 mi
982638b
Lyman, WA · 13 mi
982238b
Arlington, WA · 13 mi
982848b
Sedro Woolley, WA · 14 mi

All 2 ZIP codes in Mount Vernon → · Washington planting zones →

Questions about 98274

What planting zone is ZIP code 98274?

ZIP code 98274 (Mount Vernon, WA) is in USDA hardiness zone 8b on the 2023 map: the coldest night of an average winter reaches 15 to 20 °F (−9.4 to −6.7 °C).

When is the last frost in Mount Vernon, WA?

The median last spring frost (32 °F) near 98274 is April 22; after May 6 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Arlington station.

When is the first frost in Mount Vernon, WA?

The median first fall frost near 98274 is October 19, giving a median frost-free growing season of 181 days.

When should I plant tomatoes in 98274?

Start tomato seeds indoors around Feb 25 – Mar 11 and set transplants outside around Apr 29 – May 13, one to three weeks after the median last frost.

How much rain and snow does 98274 get?

About 49 inches of precipitation a year and 4 inches of snowfall (NOAA 1991–2020 normals, Arlington station).

How hot do summers get in Mount Vernon, WA?

The average high peaks at 78 °F in August, with about 5 days a year at 90 °F or more.

What kind of soil does 98274 have?

The USDA soil survey maps Chuckanut at the center of ZIP 98274: slightly decomposed plant material, well drained, pH about 4.5 (strongly acidic).

Did spring come early in Mount Vernon, WA in 2026?

Spring leaf-out near 98274 came on Feb 22 in 2026, 27 days earlier than the 1991–2020 average (Mar 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mount Vernon, WA?

Long-day onions: the longest day near 98274 is 16 h 06 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 98274 change?

Yes. The 2012 USDA map put 98274 in zone 8a; the 2023 map puts it in zone 8b. The newer map uses 1991–2020 data and more weather stations.